Time series collected from 2004 to 2020 at an oceanographic station located at the westernmost sill of the Strait of Gibraltar to monitor the Mediterranean outflow into the North Atlantic have been used to give some insights on changes that have been taking place in the Mediterranean basin. Velocity data indicate that the exchange through the Strait is submaximal (that is, greater values of the exchanged flows are possible) with a mean value of −0.847 ± 0.129 Sv and a slight trend to decrease in magnitude (+0.017 ± 0.003 Sv decade−1). Submaximal exchange promotes footprints in the Mediterranean outflow with little or no-time delay with regards to changes occurring in the basin. An astonishing warming trend of 0.339 ± 0.008°C decade−1 in the deepest layer of the outflow from 2013 onwards stands out among these changes, a trend that is an order of magnitude greater than any other reported so far in the water masses of the Mediterranean Sea. Biogeochemical (pH) data display a negative trend indicating a gradual acidification of the outflow in the monitoring station. Data analysis suggests that these trends are compatible with a progressively larger participation of Levantine Intermediate Water (slightly warmer and characterized by a pH lower than that of Western Mediterranean Deep Water) in the outflow. Such interpretation is supported by climatic data analysis that indicate diminished buoyancy fluxes to the atmosphere during the seven last years of the analyzed series, which in turn would have reduced the rate of formation of Western Mediterranean Deep Water. The flow through the Strait has echoed this fact in a situation of submaximal exchange and, ultimately, reflects it in the shocking temperature trend recorded at the monitoring station.

The oceanography of the Alboran Sea (AS) has been the subject of intensive research for decades. Chief among the reasons for this interest is the variety of physical processes taking place in the basin, spanning from coastal upwelling, dynamic of density fronts, internal waves, and strong meso- and submesoscale turbulence. Historical fieldwork and an increasing number of numerical studies in recent years have led to a more complete—although more dispersed—description and knowledge of process dynamics in the AS and their role in shaping primary productivity and regional fisheries resources. In this review, we summarize and put together old and new research to get an updated picture of the AS circulation and its variability at different time scales, with an emphasis on physical–biological interactions. As part of the review, we identify gaps in our understanding regarding the physical drivers for seasonal and for rapid transitions between the most recurrent one-gyre and two-gyre modes of circulation of the AS. We also point at possible research strategies based on end-to-end regional biophysical modeling to gain new insights into past and present physical control on fisheries resources and for assessing plausible climate change impacts on the AS ecosystem.

The blackspot seabream (Pagellus bogaraveo) is a benthopelagic fish species highly appreciated by consumers and an important target of the Spanish and Moroccan fisheries in the transcontinental waters of the Strait of Gibraltar area. It is also one of the most exploited resources of the region, which has led to a situation of overexploitation and a notable drop of catches. To gain insight into the sustainability of this resource and certain patterns of the spatial adaptation of the species, a high‐resolution circulation model coupled to a Lagrangian tracking module has been employed to investigate the dispersal pathways of blackspot seabream, using eggs and larvae (early‐life‐stages, ELS) as purely passive particles advected by currents. Several spawning scenarios consisting of different spatial (depths and sites) and temporal (tidal phase and strength) initial conditions have been analyzed to identify the most likely pathways of ELS dispersion. Eastward transport by the Atlantic Jet exiting the Strait of Gibraltar is the most influencing process in that dispersion. Regarding temporal fluctuations, fortnightly tidal modulation is the prevailing factor to determine the horizontal paths of the ELS, spring tides being the cause of the greatest scattering of propagules. Spawning depth in the Strait of Gibraltar is a critical condition, as revealed by the model sensitivity tests. Potential implications of the results of the study to improve the assessment and management of this species are discussed.

Presently, the Strait of Gibraltar is undergoing an unprecedented invasion of the alien alga Rugulopteryx okamurae of North Pacific origin. According to the scarce literature, the algae first settled in the south shore, probably following commercial exchanges with French ports where it was accidentally introduced together with Japanese oysters imported for mariculture. There is no certainty, however, that the algae first colonized the south shore of the Strait and, from there, spread to the north. It could well have been the opposite. Whatever the case, it spread all over the Strait and surrounding areas with amazing rapidity. Human-mediated vectors (algae attached to ship hulls or fishing nets, for example) can be behind the spread from the shore initially settled to the algae-free shore on the opposite side. But it could also have happened by means of hydrodynamic processes without direct human intervention. This possibility is assessed in this paper by revisiting historical current meter profiles collected in the Strait of Gibraltar searching for secondary cross-strait flows. All the stations present an intermediate layer of northward cross-strait velocity near the interface of the mean baroclinic exchange along with a surface layer above of southward velocity, whose lower part also overlaps the interface zone. The first one would back the south-to-north transport of algal fragments, the second one, the north-to south. In both cases, algae must reach the depth of the interface. The vertical velocity field in the area, which far exceeds the small sedimentation velocity of the algae, allows their vertical displacements throughout the water column. Its endurance to survive under the weak or no light conditions that will prevail during the cross-strait transport and its capability of reactivating the metabolism after this unfavorable period, offers chances for colonizing the opposite shore. Therefore, the propagation of the algae by hydrodynamic processes, without human intervention, cannot be ruled out.